1. Field of the Invention
The present invention relates to an apparatus for producing an oxygen enriched gas, particularly, oxygen enriched air, from atmospheric air, and more particularly, relates to an oxygen enriching apparatus adapted for use in the treatment of patients suffering from ailments such as asthma, emphysema, and chronic bronchitis, and provided with a means for regulating a concentration of oxygen in the oxygen enriched gas.
2. Description of the Related Art
The adoption of oxygen inhalation for the treatment of patients suffering from respiratory ailments such as asthma, emphysema, and chronic bronchitis is well known, and such an oxygen inhalation treatment employs an oxygen gas or oxygen enriched air. Heretofore, the oxygen gas or the oxygen enriched air has been supplied by conventional gas cylinders, but recently an oxygen enriching apparatus producing an oxygen enriched air from the atmospheric air has been developed and is in practical use. This apparatus is convenient to use and easily maintained.
There are two types of the above oxygen enriching apparatus; a membrane separation type oxygen enriching apparatus as disclosed in U.S. Pat. No. 4,174,955, which utilizes a membrane permitting a selective permeation of oxygen more readily than nitrogen, and an adsorbing type oxygen enriching apparatus as disclosed in, e.g., U.S. Pat. No. 4,576,614 and Published European Patent Application No. 0 135 936, which employs an adsorbent adsorbing nitrogen more readily than oxygen. The membrane separation type oxygen enriching apparatus obtains an oxygen enriched gas with a 40 volume % concentration of oxygen, due to the selective permeation property of the membrane. The adsorbing type oxygen enriching apparatus obtains an oxygen enriched gas with a 90 volume % concentration of oxygen, due to a stable separation of oxygen or nitrogen from the source gas, such as the atmospheric air.
In the treatment of patients suffering from respiratory ailments by oxygen inhalation, either a low oxygen concentration gas with approximately a 40 volume % of oxygen or a high oxygen concentration gas with approximately a 90 volume % of oxygen is required, depending on the condition of the patient. Thus, in the conventional oxygen inhalation treatment using an oxygen enriching apparatus, the membrane separation type oxygen enriching apparatus is used for supplying patients with a low oxygen concentration gas, and the adsorbing type oxygen enriching apparatus is used for supplying patients with a high oxygen concentration gas. That is, at clinical sites such as hospitals, both the membrane oxygen enriching and adsorbing type oxygen enriching apparatuses must be installed to carry out an oxygen inhalation treatment and this is very inconvenient.
The adsorbing type oxygen enriching apparatus as disclosed in the afore-mentioned U.S. Pat. No. 4,576,614 or Published European Patent Application No. 0 135 936 is provided with a means for changing an oxygen or nitrogen concentration as required. However, this means for changing an oxygen concentration or nitrogen concentration is difficult to operate.
Further, when the oxygen inhalation treatment is carried out, the flow rate of the oxygen enriched gas supplied from an oxygen enriching apparatus to the nasal cavities of a patient must be controlled to an appropriate level, and in the conventional oxygen enriching apparatus, a rotameter having a float is employed to measure the flow rate of the oxygen enriched gas. However, the float of the rotameter fluctuates and produces an irregular flow, and thus it is difficult for the patient to set the flow rate to a required level or to read the scale indicating the flow rate of the gas. Therefore, there has been a need for the development of a flow rate measuring device for an oxygen enriching apparatus, in which it is easy to set a flow rate and the flow rate is clearly indicated.
Moreover, in the case of the conventional adsorbing type oxygen enriching apparatus used to produce an oxygen enriched gas with a 90 volume % concentration of oxygen, when a flow rate control valve is widened so as to increase an amount of flow of the oxygen enriched gas from the outlet of the apparatus, the oxygen concentration is unfavorably varied. Accordingly, the conventional adsorbing type oxygen enriching apparatus is impractical.